Brian Mockenhaupt (thanks, Dan Stockman): Near the end of June, the weather patterns over Arizona shift. Wet air from Mexico flows in from the south, replacing the dry air that pushes in from the southwest during the spring. This is the summer monsoon, from the Arabic word mausim, for season: a shift in the wind. Thunderstorms gather along the Mogollon Rim, a 200-mile escarpment that stretches across central Arizona at the southern edge of the Colorado Plateau. As they build, the storms suck in desert heat and moist air and then move out over lower-lying areas, where they dump inches of rain.
Last summer, on Friday, June 28, one of the first thunderstorms of the season gathered along the Mogollon Rim, but because the season was young, the storm didn’t draw much moisture from the newly arriving Mexican air. Instead, it arose mainly as an unstable swirling mass of hot and cold air, a turbulent mix that generated 100-mph updrafts within the clouds.
From the Mogollon Rim, the storm moved west. As it did, its turbulence rammed and scraped ice crystals together in the storm clouds. Atoms in the clouds stripped electrons from one another and generated an electrical field—the perfect conditions for lightning. Most lightning jumps between or within clouds, but sometimes a tiny filament of charged particles streams down and meets with oppositely charged particles that are drawn up to them from an elevated point on the Earth’s surface: a tree on a mountaintop, for example. As soon as the gap is closed, a light switch is turned on, and the filament glows: electricity surges in massive amounts between the two points, creating a plasma channel that can heat the surrounding air to more than 50,000 degrees, five times hotter than the surface of the sun.